(1. ) Field Of The Invention
The present invention relates to rosin ester resins modified with a hydroxy functional polymer such as an acrylic polymer. More specifically, this invention relates to acrylic polymer modified esters of rosin, methods for preparing the modified rosin, as well as the use of an acrylic polymer modified rosin ester in vehicles for gravure printing inks.
(2. ) Description Of The Prior Art
Modified rosins have come into widespread use as binders in vehicles for gravure printing inks. However, these inks are usually quite costly. In addition, with the development of the printing arts, the speeds of printing have become increasingly high, and requirements for various ink properties such as gloss, drying properties, blocking holdout, firm formation, film toughness (resistance to abrasion), reducibility and printability, color development, resistance to static movement or rub are of primary importance to the resin supplier. All of these properties are affected by the resin or binder used to formulate these inks.
Prior to this invention rosins have been modified with one or more (in succession) or with a combination of dienophiles, and/or with phenolic resins and often followed by esterification in attempts to produce tougher, glossier inks that are resistant to rub. The beneficial product characteristics provided by rosin esters for various uses have led to the development of many esterification procedures, particularly treatments with polyhydric alcohols. U.S. Pat. No. 2,369,125 to Jones, et al. and U.S. Pat. Nos. 2,572,086 and 2,590,910 each to Wittcoff, et al. teach rosin esterification with glycerol and pentaerythritol, among other polyhydric alcohols.
In U.S. Pat. No. 2,478,490 to Krumbhaar, there is disclosed rosin-modified, phenol/formaldehyde resins containing rosin esterified by polyhydric alcohols and reinforced by polybasic acids of the maleic type which are useful in printing inks. These rosin-modified phenol/formaldehyde resins and rosin-modified maleic esters are prepared by heating rosin together with phenol/formaldehyde condensates, with maleic-type polybasic acids, or both, and subsequently esterifying with polyhydric alcohol.
Japanese Patent 62-265,376 to Toray Ind. discloses printing ink compositions containing rosin modified phenolic resins with a polyfunctional acrylate. The Japanese patent does not disclose a modified resin that has been esterified. U.S. Pat. No. 4,693,846 to Piccirilli, et al. discloses a urethane-modified dimerized rosin ester for use in lithographic printing inks and coatings.
There exists a need in the art of gravure printing for an ink which is inexpensive and exhibits good properties in such parameters as film toughness (resistance to abrasion), blocking, color development, gloss, resistance to static movement or rub, high hold out and excellent printability when printed on a given substrate. All of these properties are affected by the resin or binder used to formulate the ink.
Accordingly, it is a primary object of this invention to provide rosin resins and resinates which produce superior gravure printing inks and avoid unsatisfactory physical properties.
Another object of this invention is to provide improved modified rosin resins and resinates for use in printing ink formulations.
Yet another object of this invention to provide a process for making modified rosin resins and resinates which are particularly useful as a component of printing ink vehicles.
It is a further object of this invention to provide a gravure printing ink containing a modified rosin or resinate as a binder which exhibits improved film toughness, gloss and Sutherland rub.
Other objects, features and advantages of the invention will be apparent from the details of the invention as more fully described and claimed.